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C L Seidel

Publications and source records attributed to C L Seidel.

At least 37 records · Page 2Linked to original sources
PubMed1991

Serotonin-induced Na+/K+ pump stimulation in vascular smooth muscle cells. Evidence for coupling to multiple receptor mechanisms.

Exposure of cultured canine femoral artery vascular smooth muscle cells to serotonin (5-HT) caused a 3.6-fold stimulation of ouabain-sensitive 86Rb uptake. The 5-HT2 receptor antagonist, ketanserin, partly blocked the 5-HT-mediated Na+/K+ pump stimulation and the 5-HT1/5-HT2 receptor antagonist, methiothepin, completely blocked the response, suggesting that both 5-HT1 and 5-HT2 receptors play a role in the 5-HT-mediated Na+/K+ pump activation. Second messengers generated by 5-HT2 receptor-mediated phosphoinositide hydrolysis, Ins(1,4,5)P3 and diacylglycerol were implicated in the stimulatory action of 5-HT on the vascular Na+/K+ pump. Like some other contractile agonists, 5-HT activated a Na+ influx pathway which caused Na+/K+ pump stimulation by increasing the rate-limiting substrate. The maximum stimulation of Na+ influx by 5-HT was 2.5-fold. The 5-HT-stimulated Na+ influx was totally blocked by methiothepin but only 29% inhibited by ketanserin, indicating that most of the Na+ influx was mediated by the 5-HT1 receptor. The 5-HT-stimulated Na+ influx was substantially inhibited by 50 microM dimethylamiloride, suggesting that the Na+ influx pathway stimulated by 5-HT was Na+/H+ exchange. BAPTA/AM 1,2-[bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, tetra (acetoxymethyl) ester], an intracellular Ca++ chelator, partly blocked 5-HT-stimulated Na+ influx and ouabain-sensitive 86Rb uptake, suggesting that Ca++ is an important mediator of these responses. These data suggest that: 1) 5-HT, in addition to its well known activity as a contractile agonist, can stimulate the electrogenic Na+/K+ pump which, in theory, would tend to oppose contraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Focal toxicity of oxysterols in vascular smooth muscle cell culture. A model of the atherosclerotic core region.

Cell necrosis and reactive cellular processes in and near the atherosclerotic core region might result from short-range interactions with toxic lipids. To model these interactions in cell culture, focal crystalline deposits of cholestane-3 beta,5 alpha,6 beta-triol, 25-OH cholesterol, and cholesterol were overlaid by a collagen gel, on which canine aortic smooth muscle cells were seeded. Oxysterols, but not cholesterol, caused focally decreased plating efficiency and cell death, leading to the formation of a persistent circular gap in the cell culture. Cholestanetriol was largely removed from the culture dishes over 3 to 4 weeks, whereas cholesterol and 25-OH cholesterol were largely retained. Smooth muscle cells were motile even in proximity to oxysterol crystals, with occasional suicidal migration toward the crystals. Chemoattraction, however, could not be demonstrated. Despite toxicity, cholestanetriol did not appear to alter the fraction of cells exhibiting 3H-thymidine uptake, even in areas close to the crystals. Thus, oxysterols may be toxic to some cells, without causing major impairment of the migration and proliferation of nearby cells. This would allow the simultaneous occurrence of cell death and proliferation evident in atherosclerosis.

Animals↗
PubMed1989

Quantitative and qualitative heterogeneity in smooth muscle myosin heavy chains.

Previous studies have shown that smooth muscle myosin consists of two heavy chains (MHCs) of unequal molecular weight; however, it is not clear whether there are intermuscle, inter- and intraspecies differences in the MHCs. The purpose of these experiments was to quantitatively and qualitatively compare MHCs in different smooth muscles. Extracts of bovine aorta (BAo), dog saphenous vein (dSV) and femoral artery (dFA), and rat aorta (rAo), femoral artery (rFA), carotid artery (rCA), ileum (rGI) and uterus (rUt) were electrophoresed on 5% polyacrylamide-1% SDS gels. All tissues exhibited two MHCs with molecular weights of 207,000 (MHC1) and 204,000 (MHC2) daltons. In all cases the proportion of total MHC made up by MHC1 was greater than that by MHC2. Based on their relative proportions (MHC1:MHC2), the tissues fell into one of three groups: (1) 55:45 - rAo, rCA, dFA; (2) 60:40 - dSV, BAo, rGI; and (3) 65:35 - rUt, rFA. Group 1 differed significantly from group 3 in the proportion of each MHC. One dimensional peptide maps indicated that BAo, dSV and dFA were similar while subtle differences existed between rUt and rAo. Differences between rUt and rAo were also observed in their cross-reactivity to a monoclonal antibody to smooth muscle MHC, confirming the differences seen on peptide maps. These results indicate that there are intertissue and inter- and intraspecies differences in smooth muscle MHCs. The significance of these differences to muscle function remains to be determined.

Animals↗
PubMed1989

Intracellular Na+ regulation of Na+ pump sites in cultured vascular smooth muscle cells.

Enzymatically dispersed cells from canine saphenous vein and femoral artery were grown in fetal calf serum and studied at day 0 (freshly dispersed) through confluence in primary culture. Intracellular Na levels (Nai), but not intracellular K (Ki), were increased after 24 h in culture and then decreased to a steady state by 4 days. Na+ pump site number [( 3H] ouabain binding) increased through day 3 and remained elevated. Nai was still elevated at 2 days when the Na+ pump site number began to increase. Total pump turnover (maximum ouabain-inhibited 86Rb uptake) reflected the increase in Na+ pump site number. These key events precede the observed increases in both protein production and cellular proliferation. If the same cells are maintained in defined medium, without fetal calf serum, Nai, Ki, and the number of [3H]ouabain binding sites do not change with time. These data are consistent with the suggestion that the initial mitogenic response of vascular smooth muscle cells to fetal calf serum involves an increased Na+ influx, and a Nai accumulation, caused by low Na+ pump density. The synthesis of new pump sites effects a decrease in the accumulated Nai, which may be related to cell proliferation.

Animals↗
PubMed1989

Vascular myosin expression during cytokinesis, attachment, and hypertrophy.

Primary cultures of canine saphenous vein smooth muscle cells downregulate the expression of the two muscle myosin heavy chains (mMHC) and upregulate the expression of a nonmuscle myosin heavy chain (nmMHC) when maintained in medium containing 10% fetal calf serum (FCS). The cellular function and control of these changes in contractile protein expression are not known. The purposes of these experiments were to determine whether the expression of nmMHC was required for cytokinesis, whether cell attachment stimulated nmMHC expression, and whether during changes in total myosin production the relative amounts of the two mMHCs remained constant. Primary cultures were maintained in FCS, in a serum-free defined medium (SFM), or after 2 days in SFM switched to FCS to induce proliferation and changes in myosin expression. nmMHC expression occurred before cytokinesis if cells were placed directly in FCS, whereas it occurred after cytokinesis if growth-arrested cells were exposed to FCS. The position of the cell in the cell cycle was responsible for these differences, and the temporal correlation of cell-cycle progression and nmMHC expression indicated that expression occurred during G1. Cells that remained unattached in the presence of FCS or attached in SFM did not express nmMHC. During net production or loss of mMHC by growth in SFM or FCS, respectively, the relative amounts of the two mMHC remained constant. These results suggest that 1) the expression of nmMHC requires the combined effect of FCS and attachment, 2) it occurs in cells progressing through G1 but is not required for cytokinesis, and 3) during changes in net myosin production, the two mMHC are coregulated.

Animals↗
PubMed1988

Effect of seeding density and time in culture on vascular smooth muscle cell proteins.

The purpose of this work was to determine the effect of seeding density and time in culture on quantitative and qualitative characteristics of myosin in primary cultures of vascular smooth muscle cells (VSMCs). Enzymatically dispersed VSMCs from femoral arteries and saphenous veins of adult dogs were seeded at a density of 10(3)-10(5) cells/cm2 and assayed after 7 days or at 10(5) cells/cm2 and assayed between 1 and 10 days. Myosin, actin, and total protein contents as well as electrophoretic and immunoreactive characteristics of myosin heavy chains (MHCs) were determined. Total and contractile protein contents were independent of seeding density and increased with time in culture. Freshly dispersed cells exhibited two MHCs (MHC-1 and MHC-2) but, within 24 h after culturing, only cells attached to the dish expressed a third protein band (MHC-3), which had electrophoretic mobility and immunoreactivity similar to purified platelet MHC. MHC-3 appeared before onset of cell division and, by 4 days in culture when cells were proliferating, became the dominant MHC form. Loss of MHC-1 and MHC-2 could be prevented by growing cells in a serum-free, defined media that prevented proliferation. These data indicate that seeding density does not affect myosin content, but that with time in culture expression of a MHC with characteristics similar to nonmuscle myosin occurs. Expression of MHC-3 is associated with cell attachment, whereas loss of MHC-1 and MHC-2 requires proliferation.

Actins↗
PubMed1988

Sodium pump stimulation by activation of two alpha adrenergic receptor subtypes in canine blood vessels.

The effects of alpha-1 and alpha-2 selective adrenergic agents on sodium pump activity were investigated in intact canine femoral artery and saphenous vein by measuring ouabain-sensitive uptake of 86Rb. In both vessels, the alpha-1-selective agonist, phenylephrine, stimulated 86Rb uptake in a dose-dependent manner. The uptake was blocked by prazosin and yohimbine with the order of potency: prazosin greater than yohimbine. The alpha-2-selective agonist, clonidine, also stimulated 86Rb uptake in the saphenous vein but not in the femoral artery. The stimulation was blocked by prazosin and yohimbine with the order of potency: yohimbine greater than prazosin. The potency of phenylephrine to contract saphenous vein or femoral artery was the same as that for stimulation of ouabain-sensitive 86Rb uptake. Clonidine was 10-fold more potent as a contractile agonist than as a Na+ pump stimulant. It caused only a weak contraction in the femoral artery. Reducing extracellular sodium abolished the stimulation of 86Rb uptake by both phenylephrine and clonidine in saphenous vein. Subsequently it was shown that both agonists increased intracellular sodium levels and these increases were blocked by the alpha receptor antagonists, prazosin and yohimbine, with the same selectivity as was observed in the 86Rb uptake experiments. Sodium pump stimulation produced by both phenylephrine and clonidine was blocked by amiloride. These observations suggest that the activity of the vascular sodium pump can be regulated by both alpha-1 and alpha-2 adrenergic receptors and that the mechanism involves an influx of sodium, most likely through a stimulation of Na+/H+ exchange.

Animals↗
PubMed1987

Whole-cell and single-channel calcium currents of isolated smooth muscle cells from saphenous vein.

Whole-cell and single-channel calcium currents in enzymatically isolated dog saphenous vein cells were recorded by the patch-clamp method. Test pulses to negative potentials from holding potentials of -90 to -40 mV elicited currents that inactivated quickly and in a voltage-dependent manner (called I low for low threshold). A second calcium current persisted even at relatively positive holding potentials of -30 to -10 mV, required stronger depolarizations for maximum current, and inactivated slowly (I high for high threshold). I high transported barium more than calcium, whereas I low transported the two ions equally. Single-channel current records (90 mM barium) showed a larger conductance that activated at relatively positive potentials and a smaller (about one-third) conductance that activated at weak depolarizations. Nitrendipine suppressed I high, and the effect was voltage dependent as observed in cardiac cells, although block of resting channels was much greater in vein cells (KR approximately 10(-8) M). Exposure to the stereoisomer (-)Bay K 8644 increased I high but not I low. The (-)Bay K 8644 also increased the channel activity and prolonged the open time of the larger conductance current. Thus, two types of calcium channels, differing in potential-dependence of activation and inactivation, calcium/barium selectivity, single-channel conductance, and sensitivities to dihydropyridines were identified in smooth muscle cells isolated from a large cutaneous vein.

Animals↗
PubMed1987

Venous and arterial endothelia: different dilator abilities in dog vessels.

It has been demonstrated by other investigators that endothelium-dependent vasodilators are more effective on arterial tissue than on venous tissue. The purpose of this study was to determine if this was due to a difference in the sensitivity of arterial and venous smooth muscle to the endothelial dilator (EDRF) or to a difference in the ability of arterial and venous endothelia to release EDRF. To differentiate between these two possibilities, an in vitro "sandwich" preparation was used in which the mechanical response to endothelium-dependent dilators of a de-endothelialized vessel was determined when "sandwiched" with an endothelialized vessel. Using dog femoral artery and saphenous vein, it was determined that acetylcholine (ACh), the ionophore A23187, and thrombin were endothelium-dependent dilators of the femoral artery, but their dilatory ability was significantly less in the saphenous vein. However, if the de-endothelialized saphenous vein was "sandwiched" with an endothelialized femoral artery, both ACh and A23187 significantly relaxed the vein. No relaxation of the de-endothelialized femoral artery occurred when it was "sandwiched" with an intact saphenous vein. Sodium nitroprusside, thought to act by a mechanism similar to EDRF, relaxed equally the saphenous vein and femoral artery. These observations suggest that the difference in responsiveness between femoral arteries and saphenous veins to endothelium-dependent dilators is due more to differences in the ability of their endothelia to release EDRF than to an inability of their smooth muscle to respond to EDRF.

Acetylcholine↗
PubMed1987

Maturational changes in the pharmacological characteristics and actomyosin content of canine arterial and venous tissue.

The purpose of this study was to compare the pharmacological characteristics and actomyosin content of arterial and venous tissue at different times during development. Rings of arteries (femoral, renal, carotid, pulmonary) and veins (saphenous, pulmonary, jugular) were obtained from 1 wk, 1 month, and adult dogs, mounted at their optimal length for force development and the contractile response to potassium chloride and phenylephrine determined. The strain at optimal length was less at all ages in pulmonary artery and pulmonary and jugular veins than in other vessels. All vessels exhibited an increase in maximum contractile response with development but the increase was greater for phenylephrine. In general, the magnitude of the maximum response of the jugular and pulmonary veins and pulmonary artery was less than other vessels at all ages. The sensitivity (half maximum response) either increased or was unchanged in arteries with development, while in the veins it either decreased or was unchanged. The relaxant effects of verapamil and isoproterenol were determined on potassium chloride contracted vessels. Arterial tissue was minimally responsive to isoproterenol at all ages while venous tissue either increased its responsiveness (saphenous, pulmonary) with development or remained highly responsive (jugular). Verapamil, unlike isoproterenol, was an effective relaxant of all vessels. The actomyosin content (mg/mm) of femoral and renal arteries and saphenous and jugular veins increased with development but this increase was accompanied by a parallel increase in total protein so that the ratio (actomyosin/total protein) was unchanged. In jugular veins from adult dogs this ratio was smaller than in arterial tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Actomyosin↗
PubMed1986

Metabolic characteristics of aorta from spontaneously hypertensive and renal and deoxycorticosterone acetate-salt hypertensive rats.

The purpose of this study was to determine if any changes occurred in the basal and stimulated rates of oxygen consumption and lactate production of thoracic aortas from spontaneously hypertensive rats (SHR) and renal and deoxycorticosterone acetate (DOCA)-salt hypertensive rats, and, if so, whether these changes were similar in these three models of hypertension. Rings of thoracic aorta were placed in an isothermic (37 degrees C) muscle bath, and isometric tension development, oxygen consumption, and lactate production were measured. The results indicated that under basal conditions oxygen consumption, but not lactate production, was higher in aortas from all three hypertensive models; the elevation above control was greatest in the renal model (95%) and smallest in SHR (34%). On stimulation with 60 mM KCl, a significant increase in oxygen consumption above basal value occurred in all aorta samples (p less than 0.05); however, lactate production was increased above basal only in aortas from hypertensive animals. Only in aortas from renal and DOCA-salt models was the rate of oxygen consumption during stimulation significantly greater than that of their normotensive controls (p less than 0.05). Developed active stress in response to KCl was the same in all groups, and when the change in lactate production or oxygen consumption was expressed relative to the amount of active stress developed, no differences were observed. These results suggest that, 1) compared to values in aortas from normotensive animals, only the basal rate of oxygen consumption is higher; 2) this higher level of basal metabolic activity is not associated with an alteration in the metabolic cost of force development.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Changes with hypertension and maturation in the response of stomach fundus to acetylcholine.

The purpose of these experiments was to compare the contractile response to ACh of stomach fundal strips from hypertensive (SHR) and normotensive (WKY) rats during the development of hypertension. The results indicate that the reactivity to ACh is the same in fundal strips from young SHR and WKY rats; however, with maturation strips from WKY rats undergo a reduction in responsiveness which does not occur in the SHR. Therefore, strips from older SHR rats are more reactive to ACh than are those from age matched WKY rats.

Acetylcholine↗
PubMed1984

Adaptation of canine saphenous veins to grafting. Correlation of contractility and contractile protein content.

Saphenous veins are used extensively to replace stenotic coronary arteries. However, the contractile and biochemical adaptations of grafted veins are unknown. The three purposes of this work were to characterize the contractile properties of grafted veins, to determine whether altered contractile characteristics were associated with quantitative changes in actin, myosin and collagen, and to determine which changes were associated with the surgical procedure and which with placement in the arterial circulation. Canine saphenous veins were removed and returned to their original location (venous autograft), while others were used to replace a segment of femoral artery (arterial graft). The grafts were removed 1, 4, and 8 weeks later and compared with the contralateral saphenous vein. Both graft types exhibited an increase in sensitivity to norepinephrine but not to potassium chloride. The venous autograft exhibited a reversible reduction in myosin content and in maximum contractile response (force/cross-sectional area) to potassium chloride and norepinephrine. In contrast, the arterial graft exhibited increased wall thickness and content of all measured proteins and decreased maximum contractile response. The latter occurred even though there was an increase in the net production of actin and myosin. Expressing the maximum contractile response in terms of the myosin content did not normalize the contractile response. These results suggest that, except for the elevated sensitivity to norepinephrine, the vein is capable of recovering from the effects of surgery within 8 weeks; however, placement of the vein in the arterial circulation delays this recovery and initiates a hypertrophic response that includes an attenuation of contractile function.

Adaptation, Physiological↗
PubMed1983

Differences in K+-induced relaxation of canine femoral and renal arteries.

The extent and initial rate of potassium-induced relaxation of canine femoral and renal arteries were measured as a function of potassium concentration [K+]. Both parameters were greater in the renal artery at low [K+]; the dissociation constant for potassium of the femoral artery was greater than that of the renal artery. If potassium-induced relaxation reflects sodium pump activity, then these data indicate that the sodium pumps of the two arteries are different. When we repeated the above experiments in a lowered sodium medium, the rate and extent of potassium-induced relaxation and the apparent affinity for potassium increased in the femoral artery as predicted by kinetic models based on both isolated Na+-K+-ATPase and intact tissue. The same parameters in the renal artery, however, were unaffected by lowered sodium. These results and those presented in the companion paper [Am. J. Physiol. 245 (Heart Circ. Physiol. 14): H604-H609, 1983] can be interpreted to mean that potassium-induced relaxation does not accurately reflect sodium pump function in canine renal arteries.

Animals↗
PubMed1983

Ouabain binding, Na+-K+-ATPase activity, and 86Rb uptake of canine arteries.

In a previous report [Am. J. Physiol. 245 (Heart Circ. Physiol. 14): H598-H603, 1983] we measured potassium-induced relaxation of canine femoral and renal arteries as an index of sodium pump function and concluded that it may not be an accurate measure. In this report, the sodium pumps of femoral and renal arteries were examined using three separate approaches to compare sodium pump function more directly. The number of pump sites in subcellular fractions was measured using [3H]ouabain binding. No differences were observed (femoral artery 14.5 +/- 4.8 pmol/g wet wt; renal artery 17.4 +/- 6.5). Similarly, there was no difference in ouabain-inhibitable Na+-K+-ATPase activity in NaI-treated microsomal fractions of these arteries (femoral artery 3.10 +/- 0.65 mumol Pi X mg-1 X h-1; renal artery 3.42 +/- 0.23). Finally, sodium pump function was measured using the ouabain-inhibitable 86Rb uptake method. The rate of ouabain-inhibitable 86Rb uptake was found to be identical for the two arteries, as were the dissociation constants of the two arteries for rubidium. However, in the presence of 3.5 microM norepinephrine, the rate of 86Rb uptake in the renal artery was greater than that of the femoral artery. We conclude that, under resting conditions, the sodium pumps of femoral and renal arteries are identical, whereas in the presence of norepinephrine, the renal artery sodium pump is not rate limiting with respect to contractility. These data have significant implications with regard to the use of potassium-induced relaxation as an index of sodium pump activity.

Animals↗
PubMed1983

Doppler measurement of myocardial thickening with a single epicardial transducer.

To eliminate the need for intramyocardial transducers in measuring regional left ventricular (LV) function we have developed a pulsed Doppler technique utilizing a single epicardial transducer. Wall thickening is evaluated by digitally integrating the velocity of myocardial layers passing through the sample volume located at a selected depth. Thickening fraction (TF) can then be estimated by dividing the systolic excursion by the sample volume depth. The Doppler method was compared with the transit-time method in three acute dogs by placing the 4-mm-diameter epicardial Doppler transducer over a 2-mm-diameter endocardial crystal tunneled through the LV wall. With the sample volume set to 1 mm less than the minimum LV thickness, simultaneous measurements of TF by the Doppler and transit-time methods showed good agreement (r = 0.95) during control, ischemia, volume overload, shock, and anoxia. In 28 chronically instrumented piglets signals were obtained for longer periods with Doppler transducers than with transit-time segment-length crystals. We conclude that the Doppler technique provides a high-fidelity wall thickening waveform and a good estimate of TF with minimal disturbance to the ventricle and that the technique is suitable for use in both acute and chronically instrumented animals.

Animals↗
PubMed1980

Skeletal muscle protein and amino acid metabolism in hereditary mouse muscular dystrophy. Accelerated protein turnover and increased alanine and glutamine formation and release.

Interactins between skeletal muscle protein and amino acid metabolism were investigated using C57BL and 129ReJ mice with hereditary muscular dystrophy. On incubation, hind limb muscle preparations from dystrophic mice released large quantities of amino acids, particularly alanine and glutamine which were increased 70% and 40% compared to muscles from carrier or control mice. The increased alanine release did not result from altered alanine oxidation to CO2 or reincorporation into protein. Alanine and glutamine formation from added amino acids were equal with dystrophic and control muscles. Incorporation in vitro of leucine, alanine, and glutamate into proteins of dystrophic muscle was 3- to 7-fold greater than control muscle, and the incorporation in vivo of [3H]- or [14C]arginine into muscle proteins was greater in extent and earlier in time with dystrophic as compared to control muscle. Proteins were also labeled in vivo using [guanido-14C]arginine. On incubation of these muscles in vitro, a 100% greater loss of label from protein was observed with dystrophic as compared to control preparations, and the appearance of label in the media was correspondingly increased. Sodium dodecyl sulfate-gel electrophoresis of dystrophic skeletal muscle showed numerous protein bands to be reduced in density, but autoradiographic studies demonstrated that these same bands were more highly labeled in vitro by [35S]methionine in dystrophic than in control muscle. Although insulin stimulation of glucose uptake was markedly blunted in dystrophic muscle, insulin inhibited alanine and glutamine release equally from both control and dystrophic muscle. These data indicate that alanine and glutamine formation and release are increased in hereditary mouse muscular dystrophy. An accelerated degradation and an increased resynthesis of many muscle proteins were also observed in dystrophic compared to control animals. This increased proteolysis may account for the increased alanine and glutamine formation in dystrophic muscle.

Actins↗